Technical Field
The invention relates to a method for drying laundry, wherein air for drying the laundry is heated by a burner and, at least during a part of the drying operation, at least a part of the air used to dry the laundry is fed back to the burner as recirculating air, if need be together with fresh air, and to a dryer for laundry, comprising a drum for receiving the laundry to be dried and comprising at least one burner for heating air which serves for the drying.
Prior Art
Dryers for commercial laundries possess at least one burner, preferably a gas burner, for heating air which is used for drying. The air heated by the burner is passed through a preferably rotationally drivable drum containing the laundry to be dried. The air here absorbs moisture from the laundry to be dried. The moist air is afterwards led as waste air into the open and/or is fed back as recirculating air to the at least one burner and reheated by this.
At the beginning of the drying, the air leaving the drum contains the most humidity. This air cannot, or can only in small part, be reused as recirculating air. It must therefore, at least for the most part, be passed out of the dryer. At the beginning of the drying, only a small amount of recirculating air is therefore being carried. A large amount of fresh air is then fed, at least for the most part, via the burner to the dryer. As a result of this very large fresh air component, the at least one burner gets sufficient combustion air. At the conclusion of the drying operation, air having only a small amount of humidity leaves the drum. A relatively large amount of recirculating air and only a small amount of fresh air are then fed to the burner. The at least one burner then contains only very little fresh air or no fresh air at all, with the result that the burner works uneconomically. In many cases, an incomplete combustion with undesirable soot formation can ensue.
The object of the invention is to provide a method and a dryer for drying laundry, which can be operated with a relatively large recirculating air component, or with only recirculating air, economically and without negative impacts on combustion.
A method for the achievement of this object is a method for drying laundry, wherein air for drying the laundry is heated by a burner and, at least during a part of the drying operation, at least a part of the air used to dry the laundry is fed back to the burner as recirculating air, if need be together with fresh air, characterized in that the fresh air is transported to the burner at least during a part of the drying process. According to this, the fresh air is transported to the at least one burner at least during a part of the drying process. As a result of the active transport of fresh air to the burner, the fresh air is virtually blown or forced into the burner. A type of charging of the burner with fresh air occurs. As a result, the burner is also then supplied with sufficient fresh air if the recirculating air is returned in full or for the most part to the at least one burner without this adversely affecting the combustion. The drying can hence be realized with more recirculating air than previously. The inventive method thereby provides more economical drying.
A further advantageous embodiment of the method provides for, where necessary, feeding fresh air to the recirculating air after the recirculating air has been warmed by the respective burner. This happens before the warmed recirculating air has reached the laundry to be dried. In this way, only that quantity of fresh air which is necessary to the optimal operation of the burner needs to be fed to this same. If required, additional fresh air can be added directly to the warmed recirculating air, which can lead to more economical drying by, for example, increasing the amount of air available for drying the laundry.
An advantageous refinement of the method provides for the fresh air to be fed under pressure, preferably through at least one fan or a blower, to the burner. This type of transport of the fresh air to the at least one burner represents the simplest and most effective charging of the burner. Through adjustment of the fan speed, the quantity of fresh air fed to the burner can be adjusted or controlled in accordance with requirements, so that the respective burner receives as much fresh air as it requires, based on the respective recirculating air component. The burner can thus receive that quantity of fresh air which is required for the, in each drying phase, optimal operation, wherein the quantity of fresh air can be increased the greater the recirculating air component becomes which is returned to at least one burner.
A further advantageous embodiment of the method provides for, where necessary, fresh air to also be fed behind the respective burner to the recirculating air warmed by this same. This happens before the warmed recirculating air has reached the laundry to be dried. In this way, only that quantity of fresh air which is necessary to the optimal operation of the burner needs to be fed to this same. Fresh air which is required over and above this can be fed directly to the warmed recirculating air. That too leads to more economical drying.
A dryer for the achievement of the object stated in the introduction is a dryer for laundry, comprising a drum for receiving the laundry to be dried and comprising at least one burner for heating air which serves for the drying, characterized in that an air flow generator for the transport of fresh air to the burner is assigned to the at least one burner. In this dryer, it is provided to assign to the at least one burner an air flow generator for the transport of fresh air to the burner. The at least one air flow generator ensures a virtually forced supplying of fresh air to the burner, in that the air flow generator virtually pumps and/or forces fresh air into the burner, to be precise particularly when, due to a relatively large recirculating air component, the burner can no longer automatically draw in the fresh air necessary for optimal combustion.
Advantageously, the air flow generator is assigned to a supply line for fresh air to the respective burner, or to a common supply line for all burners. The fresh air can be transported by the at least one air flow generator in the at least one supply line directly to the or each burner.
A further advantageous embodiment of the dryer provides that the at least one air flow generator is configured to generate a variable stream of fresh air to the burner. As a result, the fresh air can be adjusted or controlled in accordance with requirements. A sufficient quantity of fresh air for optimal operation, in particular for optimal combustion, is thereby fed to the respective burner.
In one advantageous embodiment of the dryer, the air flow generator is configured as at least one fan. If a plurality of burners are present, a dedicated fan is preferably assigned to each burner, though one fan can also be jointly assigned to all burners. As a result, each burner can be specifically and, if necessary, individually supplied with fresh air in sufficient quantity.
A preferred refinement of the invention provides, behind the at least one burner, a preferably variable and/or closable feed opening for fresh air which can be mixed to the air warmed by the burner.
It can preferably be provided that at least one fan or at least one blower for the generation of a recirculating air flow, and/or a closable or variable waste air outlet for at least a part of the recirculating air, are provided. The at least one fan can generate a specific recirculating air flow, in particular a recirculating air flow having a desired flow velocity and/or a desired recirculating air stream. The closable or variable waste air outlet serves to regulate the recirculating air component which is returned to the at least one burner and, having been warmed, is fed from this back to the laundry. That part of the moist air which is not used as recirculating air can be led off into the open for evacuation of the moisture which accrues when the laundry is dried in the dryer.